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@tim @pfefferle @dansup

These are the reproduction steps I'm using:

* Latest WP with latest Litespeed and Activitypub plugins.
* Add Tim's initial fix to .htaccess, with [NC] for case-insensitive matching.
* Purge cache to be sure.
* curl --header "Accept: application/activity+json, application/ld+json" (WP post url)
* activitystream json should be returned
* curl --header "Accept: */* " (same url)
* Expected result is HTML, however the cached activitystream json is incorrectly returned.